R. Jimenez-Espinosa et af. : Time and Space Forecasting of Nitrate and Salinity Contents
69
Hydraulic parameters give values between 15,000 and 22,000 m 2 /day (IGME,
1982). Below sea level piezometric values are found, and the rate of continuous
decrease is about 0.75-1 m/year. In May 1989 there were some conoids with
piezometric levels of more than 10 m below sea level (Pulido et aI., 1993).
Whereas the average influx is around 15 Hm3/year, the amount of pumping water
is double.
1.3 Aguadulce Unit
This is the hydrogeological unit which has the greatest tectonic complexity. In
addition to the presence of the majority of permeable formations which occur in
the Campo de Dalias, various aquifers layers appear, separated by other levels of
low permeability, giving a true multilayer aquifer. Nevertheless, laterally some
formations could be wedged out, allowing more hydraulic connection. Such
lithological variety is reflected in the values of hydraulic parameters: 5000 to
7000 m 2 /day in Gador dolomites; around 6000 m 2 /day in Miocene calcarenites; or
200 m 2 /day in Quaternary materials. As in the previous unit, the piezometric levels
are decreasing gradually; most of the piezometric surface is below sea level,
reflecting an over exploitation. In fact, while pumping averages near 50 Hm 3 /year,
the influx is only around 15 Hm3/year.
The critical lack of balance between pumping and influx in the aquifers of Campo
de Dalias, in addition to the intensive farming activities in this area, have produced
serious consequences in the physico-chemical characteristics of this water. For this
reason, in 1986 a network was set up to check water quality by daily, weekly and
seasonal surveys (Pulido et aI., 1989). In this work we have used data from the
seasonal control network, taking into account mainly the evolution of conductivity
(a measure of salinization) and nitrates (indicating agricultural pollution).
2
EXPERIMENTAL DATA
All wells, in the different aquifers of Campo de Dalias, pump mainly in three
layers. These are layer LI composed of limestone's and dolomites from
Alpujarride Triassic sheets; layer L2 made up of Pliocene calcarenites; and layer
L3 of Quaternary detritic lithologies.
These layers can belong to each of the three different hydrogeological units.
Specifically, the Aguadulce aquifer pumps in Ll, L2 and L3; the Balanegra one in
Ll; and the Balerma-Las Marinas unit in L2 and L3. The study was carried out
analysing layer by layer in each aquifer. This is a more realistic point of view than
a treatment of the global aquifers, where all lithologies are mixed. Therefore, a
spatial revision of these three layers through time has been made.
The hydrogeochemical study of this area was carried out using two seasonal
surveys during the years 1988 to 1990, specifically, a spring survey (May) and an
autumn one (November). In this way, 110 wells spread out along Campo de Dalias
were considered. All the 110 points are distributed as follows: 44 wells belonging
to the Aguadulce aquifer, 22 to the Balanegra one, and 44 to the Balerma-Las
Marinas unit (Fig. I).
69
Hydraulic parameters give values between 15,000 and 22,000 m 2 /day (IGME,
1982). Below sea level piezometric values are found, and the rate of continuous
decrease is about 0.75-1 m/year. In May 1989 there were some conoids with
piezometric levels of more than 10 m below sea level (Pulido et aI., 1993).
Whereas the average influx is around 15 Hm3/year, the amount of pumping water
is double.
1.3 Aguadulce Unit
This is the hydrogeological unit which has the greatest tectonic complexity. In
addition to the presence of the majority of permeable formations which occur in
the Campo de Dalias, various aquifers layers appear, separated by other levels of
low permeability, giving a true multilayer aquifer. Nevertheless, laterally some
formations could be wedged out, allowing more hydraulic connection. Such
lithological variety is reflected in the values of hydraulic parameters: 5000 to
7000 m 2 /day in Gador dolomites; around 6000 m 2 /day in Miocene calcarenites; or
200 m 2 /day in Quaternary materials. As in the previous unit, the piezometric levels
are decreasing gradually; most of the piezometric surface is below sea level,
reflecting an over exploitation. In fact, while pumping averages near 50 Hm 3 /year,
the influx is only around 15 Hm3/year.
The critical lack of balance between pumping and influx in the aquifers of Campo
de Dalias, in addition to the intensive farming activities in this area, have produced
serious consequences in the physico-chemical characteristics of this water. For this
reason, in 1986 a network was set up to check water quality by daily, weekly and
seasonal surveys (Pulido et aI., 1989). In this work we have used data from the
seasonal control network, taking into account mainly the evolution of conductivity
(a measure of salinization) and nitrates (indicating agricultural pollution).
2
EXPERIMENTAL DATA
All wells, in the different aquifers of Campo de Dalias, pump mainly in three
layers. These are layer LI composed of limestone's and dolomites from
Alpujarride Triassic sheets; layer L2 made up of Pliocene calcarenites; and layer
L3 of Quaternary detritic lithologies.
These layers can belong to each of the three different hydrogeological units.
Specifically, the Aguadulce aquifer pumps in Ll, L2 and L3; the Balanegra one in
Ll; and the Balerma-Las Marinas unit in L2 and L3. The study was carried out
analysing layer by layer in each aquifer. This is a more realistic point of view than
a treatment of the global aquifers, where all lithologies are mixed. Therefore, a
spatial revision of these three layers through time has been made.
The hydrogeochemical study of this area was carried out using two seasonal
surveys during the years 1988 to 1990, specifically, a spring survey (May) and an
autumn one (November). In this way, 110 wells spread out along Campo de Dalias
were considered. All the 110 points are distributed as follows: 44 wells belonging
to the Aguadulce aquifer, 22 to the Balanegra one, and 44 to the Balerma-Las
Marinas unit (Fig. I).